fix(): ignore empty fields in security settings
fix(): ignore empty fields in security settings

- migration used to break on newly created sites which did not have any
fields filled

yashodhank/frappe,vjFaLk/frappe,RicardoJohann/frappe,saurabh6790/frappe,almeidapaulopt/frappe,RicardoJohann/frappe,frappe/frappe,vjFaLk/frappe,mhbu50/frappe,ESS-LLP/frappe,RicardoJohann/frappe,almeidapaulopt/frappe,ESS-LLP/frappe,mhbu50/frappe,saurabh6790/frappe,yashodhank/frappe,adityahase/frappe,adityahase/frappe,ESS-LLP/frappe,mhbu50/frappe,saurabh6790/frappe,frappe/frappe,yashodhank/frappe,ESS-LLP/frappe,almeidapaulopt/frappe,frappe/frappe,StrellaGroup/frappe,vjFaLk/frappe,vjFaLk/frappe,adityahase/frappe,adityahase/frappe,almeidapaulopt/frappe,yashodhank/frappe,StrellaGroup/frappe,RicardoJohann/frappe,mhbu50/frappe,StrellaGroup/frappe,saurabh6790/frappe